1. Field of the Invention
The present invention relates to a speaker system integrated with a display panel such as an image display audio output unit of a thin screen television receiver, and a method of driving the speaker system.
2. Background Art
Television receivers are becoming thinner and thinner. In October 2007, the applicant released a television receiver with a display panel part having a thickness of 3 mm using an organic EL display.
On the other hand, not typical speaker units having voice coils and cones, but speaker devices of generating sound by applying vibration to acoustic diaphragms using actuators such as super-magnetostrictive actuators have been conceived.
Specifically, JP-A-4-313999 and JP-A-2005-177688 disclose speaker devices as shown in FIGS. 18A and 18B.
In the speaker device in FIGS. 18A and 18B, a drive rod 2a of a super-magnetostrictive actuator 2 is brought into contact with the center part of a flat-plate acoustic diaphragm 1 so that its displacement direction may be perpendicular to the surface of the acoustic diaphragm 1, and thereby, the acoustic diaphragm 1 is vibrated in the direction perpendicular to the surface.
However, in the speaker device in FIGS. 18A and 18B, the amplitude of vibration becomes the maximum at the center part of the acoustic diaphragm 1 as shown by an arrow 3a and the amplitude of vibration becomes the minimum at the point apart from the point where the vibration is applied as shown by an arrow 3b. Thus, the vibration of the acoustic diaphragm 1 is inhomogeneous in the respective parts.
On the other hand, JP-A-2007-166027 discloses a speaker device as shown in FIGS. 19A and 19B.
In the speaker device in FIGS. 19A and 19B, a cylindrical acoustic diaphragm 4 is vertically supported, plural actuators 5 such as super-magnetostrictive actuators are provided at the lower end surface of the acoustic diaphragm 4 and drive rods 5a of the respective actuators are brought into contact with the lower end surface of the acoustic diaphragm 4, and thereby, the acoustic diaphragm 4 is vibrated in the direction perpendicular to the lower end surface.
In the speaker device in FIGS. 19A and 19B, the lower end surface of the acoustic diaphragm 4 is excited by longitudinal wave, vibration elastic wave propagates in the direction of the surface of the acoustic diaphragm 4, and the longitudinal wave and the lateral wave are mixed. Thus, sound wave is radiated by the lateral wave in the direction perpendicular to the surface of the acoustic diaphragm 4.
Accordingly, in the speaker device in FIGS. 19A and 19B, sound wave is radiated at the homogeneous level in any location in the axial direction of the acoustic diaphragm 4 as shown by an arrow 6a, and a sound image homogeneously localized over the entire acoustic diaphragm 4.